Reversible fan blade for a ceiling-suspended fan

ABSTRACT

An improved ceiling fan blade for use on a ceiling fan having a reversible motor and a plurality of said fan blades is provided in which each ceiling fan blade is in the shape of a trapezoid and the bottom part of the fan blade is wider than the tip of said fan blade. Each of the fan blades has two side edges that are connected to a central region of the fan blade, one of the side edges folds upwardly from the central region and the other side edge folds downwardly from the central region wherein each of the edges folds in opposite directions from the central region.

FIELD OF THE INVENTION

This invention relates to the field of ceiling fan blades.

BACKGROUND OF THE INVENTION

Ceiling-suspended fans can be generally separated into 2 categories based on the types of blade rotation.

-   -   (1) One-way rotation ceiling fan. The blade is rotated only in         one direction. The airflow is diverted downwardly.     -   (2) Reversible ceiling fan. The blade is able to rotate in two         directions. The airflow can either be diverted downwardly or         upwardly.

The ceiling fan in category (1) is for general usage. The objective is to create ventilating airflow one-way downwardly. The ceiling fan in category (2) is not only able to serve the objectives achieved by the former, but is also able to ventilate designated areas in order to help conserve thermal energy during hot or cold weather. The ceiling fan in category (2) comprises two components; a reversible electric motor and a fan blade that can create air flow in both direction of rotation.

Prior art patents exist for fan blades. For example, U.S. Pat. No. 5,575,624 shows a conventional “S” shaped fan blade for a reversible ceiling fan. The conventional “S” shaped fan blade shown in U.S. Pat. No. 5,575,624 does not provide the desirable high airflow volume that the shape of the present inventive fan blade provides. Empirical test results prove that the shape of the folded edges of the blades of the instant invention significantly outperforms the “S” shape of prior art fan blades.

The inventive fan blade may be made from wood, plastic, metal or other materials. The design is unique but normal fan capabilities still remain. In addition, the fan blade is able to rotate in the opposite direction to create airflow. The amount of airflow generated by the fan blade is almost equal in both directions. This particular fan blade is compatible with both types of ceiling fan, whether or not it has a blade bracket. The design can also be used with any ceiling fan that includes multiple blades.

SUMMARY OF THE INVENTION

What is needed is a novel and non-obvious fan blade configuration that will improve the efficiency and airflow of a reversible ceiling fan.

An improved ceiling fan blade for use on a ceiling fan having a reversible motor and a plurality of said fan blades is provided in which each ceiling fan blade is in the shape of a trapezoid and the bottom part of the fan blade is wider than the tip of said fan blade. Each of the fan blades has two side edges that are connected to a central region of the fan blade, one of the side edges folds upwardly from the central region and the other side edge folds downwardly from the central region wherein each of the edges folds in opposite directions from the central region.

The trapezoidal shape allows the blade to move as much air toward the tip of the blade as toward the bottom part of the blade but reduces the amount of energy required to move the blade by the ceiling fan motor.

The angle between the folded edges of the fan blade and the central region is in the range of approximately 1 to 30 degrees.

Each fan blade can be connected directly to a base on shaft that is connected to the reversible motor or can be connected to an intermediate bracket that is connected to the base on the shaft that is connected to the reversible motor of the ceiling fan.

The fan blades can be constructed of metal, polymer or wood. If constructed of polymer or wood, and positioned seven feet or higher above the ground, the blades are generally at least 3/16″ in thickness for safety purposes and to satisfy the requirements of the Underwriters Laboratory UL 507.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of the three of the inventive fan blades mounted on a reversible ceiling fan.

FIG. 2 a shows a top view of a fan blade of the invention including a bracket to mount to the motor of a reversible ceiling fan.

FIG. 2 b shows an end view of the fan blade shown in FIG. 2 a.

FIG. 3 a shows a top view of a fan blade of the invention that mounts directly to the motor of a reversible ceiling fan.

FIG. 3 b shows an end view of the fan blade shown in FIG. 3 a.

FIG. 4 shows an isometric view of an inventive fan blade.

FIG. 5 shows of an end view of the fan blade of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

The fan blade A of the invention is generally trapezoidal in shape. The blade A is typically wider at the bottom part of the blade 26 on the end closest to the fan and narrows toward the tip of the blade 27. The side edges 2,3 of the blade A are folded from a central region 7, one edge 2 folded upwardly and the other edge 3 folded downwardly. The preferred angle θ between the folded edges and the central region is between approximately 1 to 30 degrees (See FIG. 5).

Blade brackets 6 can be attached to the bottom part of the blade A (FIG. 2 a) or tabs 12 of the blade A can be directly mounted to the base 24 of the shaft 22 without brackets, as shown in FIG. 3 a.

The directions of airflow are illustrated in FIG. 5. When the blade A is rotated to direction 16 a, the airflow is diverted upward 16 b. When the blade A is rotated to direction 18 a, the airflow is diverted downward 18 b.

There are many advantages of the inventive blade design. One advantage is the reversible feature, which creates almost the same amount of airflow in both directions 16 b, 18 b. The tip 27 of the inventive blade A is narrower than the bottom 26, therefore less material is utilized but the amount of airflow remains the same. This reduction in blade size helps to make the blade A lighter in weight. The reduction in the weight of the blade A reduces the workload and the energy used from the fan motor 25 a. The amount of airflow can be altered by adjusting the angle of the side edges 2,3 of the blade A relative to the central region. This feature of the blade design gives more blade efficiency than any other types of fan blades currently used on ceiling fans. The preferred angle between the side edges and the central region is approximately 1 to 30 degrees. It is contemplated that the angle between the side edges and the central region be made adjustable and/or variable to fine-tune the amount of airflow produced by the inventive fan blade A. For example, the angle θ between one edge 2 and the central region 7 could be different from the angle θ between the other edge 3 and the central region 7.

Tests were conducted to compare the airflow produced by a set of the inventive fan blades with the airflow produced by a set of conventional “S” shaped fan blades. The testing was conducted on Jul. 12-13, 2006 by the Physical Testing Laboratory of the Thailand Institute of Scientific and Technological Research (TSIR) Industrial Metrology and Testing Service Centre, an independent testing laboratory. Three of each type of fan blade was tested under similar conditions on the same fan motor to obtain a valid experimental comparison of airflow performance. The dimension of the testing room was 3.8 meters wide, 10 meters long and 2.6 meters high. The distance of the ceiling fan from the ceiling was 32 centimeters. The distance of the anemometer from the fan was 150 centimeters. A Model CF-56-MI fan motor used for the testing each set of fan blades. The supply voltage to the fan motor was 120V at 60 Hz. A Davis Instrument Mfg. Co. anemometer was used to measure the airflow rate from each set of fan blades. The set of inventive fan blades showed significantly improved airflow in comparison with the set of convention “S” shaped fan blades. Specifically, when a fan blade constructed with folded edges according to the instant invention was tested against conventional “S” shaped fan blades, each having the same surface area, the test results were as follows:

Cubic Feet of Airflow Blade Tested per Minute Conventional “S” Shaped Blade 7213.48 Reversible Inventive Folded Edge Blade 8926.91

According to the independent test results, the set of inventive blades produced a surprising and unexpected resulting gain of over 23% in airflow over the set of conventional “S” shaped fan blades.

In order to comply with the ceiling fan installation regulation for fan blade suspended seven feet or more above the ground, the inventive blades that are constructed of polymer or wood, are 3/16 inches or more in thickness. This reversible blade design is able to meet this Underwriters Laboratory Section 507 requirement by using material like wood or plastic in which its thickness is not less than 3/16 inches thick and the ceiling fan motor still operates normally.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes to the angular configuration described or other changes in shape, materials or other details provided will not depart from the spirit and scope of the invention as claimed. 

1. A ceiling fan blade for use on a ceiling fan having a reversible motor and a plurality of said fan blades wherein the improvement comprises: a. Said fan blade is in the shape of a trapezoid and in which the bottom part of said fan blade is wider than the tip of said fan blade; b. Said fan blade has two side edges connected to a central region of said fan blade, one of said side edges folds upwardly from the central region and the other side edge folds downwardly from the central region wherein each of said edges folds in opposite directions from the central region.
 2. The ceiling fan blade claimed in claim 1 wherein the plurality of said blades are mounted on a base connected to a shaft that is connected to the reversible motor of the ceiling fan.
 3. The ceiling fan blade according to claim 1 wherein the angle between each of said edges and the central region is in the range of approximately 1 to 30 degrees.
 4. The ceiling fan blade claimed in claim 1 wherein said blade includes a bracket mounted on said bottom part and said bracket is mounted on a base connected to a shaft that is connected to the reversible motor of the ceiling fan.
 5. The ceiling fan blade according to claim 1 wherein the fan blade is constructed from materials selected from the group consisting of polymer and wood.
 6. The ceiling fan blade according to claim 1 wherein said fan blade is constructed of metal.
 7. The ceiling fan blade according to claim 5 wherein said blades are at least 3/16 inches in thickness. 